Abstract: Soldering experiments of fine pitch devices were carried out using IR reflow soldering method for SnAgCu and SnPb soldered joints.The results show that the tensile force of SnAgCu soldered joints is higher than that of SnPb soldered joints.By analyzing the fracture microstructure of soldered joints, it is found that the fracture mechanism of SnAgCu soldered joints is due to toughness fracture, while fracture mechanism of SnPb soldered joints includes brittle fracture and toughness fracture.Through finite element simulation, the aralytical results indicate the value of strain, stress and nonlinear strain energy of SnAgCu soldered joints are lower than those of SnPb soldered joints under temperature cyclic loading, which means the reliability of SnAgCu soldered joints is higher than SnPb soldered joints.The results of simulation accord with the experiments, which would provide a reference for theoretical investigation of lead-free solders.